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Impacts of cytoplasmic inheritance on genetic evaluations
P J Boettcher1, M T Kuhn, A E Freeman
1Department of Animal Science, Iowa State University, Ames 50011, USA.
Journal of Dairy Science
|April 1, 1996
Summary
Ignoring cytoplasmic effects in genetic evaluations can lead to inaccurate heritability and variance estimates. Properly accounting for these effects improves selection accuracy and breeding value predictions in livestock.
Area of Science:
- Animal Breeding and Genetics
- Quantitative Genetics
- Statistical Genetics
Background:
- Genetic evaluations are crucial for livestock improvement.
- Cytoplasmic effects, inherited maternally, can influence phenotypic traits.
- The impact of ignoring cytoplasmic effects on genetic evaluations is not fully understood.
Purpose of the Study:
- To investigate the consequences of omitting cytoplasmic effects in genetic evaluations.
- To assess the impact on variance component estimation, selection accuracy, genetic trend, and bull-dam selection.
- To compare sire and animal models under varying cytoplasmic variance levels.
Main Methods:
- Simulations were conducted using sire and animal models with different cytoplasmic variance levels.
- Derivative-free REML was employed for variance component estimation.
- Large-scale data files were simulated to analyze selection accuracy.
Main Results:
- Ignoring cytoplasmic effects led to overestimation of heritability (animal model) and biased permanent environmental variance.
- Properly accounting for cytoplasmic effects significantly increased selection accuracy.
- Improvements in predicted breeding values were more pronounced in cows and increased with higher cytoplasmic variance.
Conclusions:
- Cytoplasmic effects must be considered in genetic evaluations for accurate heritability and variance component estimation.
- Incorporating cytoplasmic effects enhances selection accuracy and genetic gain.
- The distinction between fixed and random cytoplasmic effects had minimal practical impact.